Systems and methods for charging a battery

ABSTRACT

The present disclosure includes a method of charging a battery. In one embodiment, the method comprises receiving, in a battery charging circuit on an electronic device, an input voltage having a first voltage value from an external power source. The battery charger is configured to produce a charge current having a first current value into the battery. The input current limit and/or duty cycle of the charger is monitored. Control signals may be generated to increase the first voltage value of the input voltage if either (i) the input current limit is activated or (ii) the duty cycle reaches a maximum duty cycle. The charger also receives signals indicating a temperature inside the electronic device and generates control signals to decrease the value of the input voltage when the temperature increases above a threshold temperature.

RELATED APPLICATIONS

The present application is a continuation application of U.S. Utilitypatent application Ser. No. 14/856,947; entitled “SYSTEMS AND METHODSFOR CHARGING A BATTERY” filed Sep. 17, 2015, which is incorporated byreference herein in its entirety.

BACKGROUND

The present disclosure relates to electronic circuits, systems andapparatuses, and in particular, to systems and methods for charging abattery.

Many modern electronic systems rely on one or more batteries for power.The batteries are typically recharged by connecting the system to apower source (e.g., an alternating current (AC) power outlet) via anAC-DC power adapter and cable, for example. FIG. 1 illustrates batterycharging in a typical electronic device. In this example, a poweradapter 102, such as an AC-DC converter, is connected to a power source101. Power adapter 102 may provide a direct current (DC) voltage andcurrent to electronic device 103 via a cable 120. Voltage and currentfrom power adapter 102 are received by a power interface, such as apower management integrated circuit (PMIC), which may convert thevoltage and current from adapter 101 to different voltages and currentsto drive various system components, such as one or more processors 111,communications electronics (e.g., radio frequency (RF) transceivers)112, and one or more input/output devices 113, such as a touch screendisplay our audio system, for example. When disconnected from anexternal power source, power interface 110 may receive voltage andcurrent from battery 114 to power the internal components, for example.

Power interface 110 may include a battery charging circuit 115 forcharging battery 114 when the battery is discharged. One problemassociated with battery chargers is power dissipation. Cable 120 mayinclude resistance leading to thermal power dissipation as well as areduction of the input voltage from the power adapter. Accordingly, thevoltage at the input of the battery charger may be less than the voltageat the output of the power adapter due to current in the cable 120. Toreduce this voltage drop, some systems may use higher adapter voltages,which will effectively reduce the amount of current required to achievethe same power level. However, higher adapter voltages can cause largerpower dissipation in battery charger circuitry. For example, highervoltages across switching transistors in the battery charger may causeincreases in power dissipation during charging due to increasedswitching losses every turn-on/off cycle. Additionally, higher inputvoltages can cause increased current ripple in a battery charger'sinductor(s), which can result in higher conduction losses and corelosses, for example. Therefore, being able to optimize power dissipationduring the battery charging process is an ongoing challenge for batteryoperated systems.

SUMMARY

The present disclosure pertains to systems and methods for charging abattery. In one embodiment, a method comprises receiving, in a batterycharging circuit on an electronic device, an input voltage having afirst voltage value from an external power source. The battery chargeris configured to produce a charge current having a first current valueinto the battery. The input current limit and/or duty cycle of thecharger is monitored. Control signals may be generated to increase thefirst voltage value of the input voltage if either (i) the input currentlimit is activated or (ii) the duty cycle reaches a maximum duty cycle.The charger also receives signals indicating a temperature inside theelectronic device and generates control signals to decrease the value ofthe input voltage when the temperature increases above a thresholdtemperature. Conversely, the same control signal can be used todecrement the input voltage when the temperature decreases below atemperature threshold.

The following detailed description and accompanying drawings provide abetter understanding of the nature and advantages of the presentdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates battery charging in a typical electronic device.

FIG. 2 illustrates an electronic device with a battery charging systemaccording to an embodiment.

FIG. 3 illustrates a method of charging a battery according to anembodiment.

FIG. 4A illustrates a method of charging a battery according to anembodiment.

FIG. 4B illustrates an example power dissipation curve.

FIG. 5 illustrates an electronic device with a battery charging systemaccording to another embodiment.

FIG. 6 illustrates an example method of charging a battery according toan embodiment.

FIG. 7 (consisting of FIG. 7A and FIG. 7B) illustrates an example methodof charging a battery according to another embodiment.

FIG. 8 (consisting of FIG. 8A and FIG. 8B) illustrates a block diagramof a circuit to control battery charging according to an embodiment.

FIG. 9A illustrates a method of charging a battery during controlledvoltage mode according to an embodiment.

FIG. 9B illustrates a method of charging a battery during controlledvoltage mode according to another embodiment.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousexamples and specific details are set forth in order to provide athorough understanding of the present disclosure. It will be evident,however, to one skilled in the art that the present disclosure asexpressed in the claims may include some or all of the features in theseexamples, alone or in combination with other features described below,and may further include modifications and equivalents of the featuresand concepts described herein.

Features and advantages of the present disclosure include batterycharging systems and methods that may optimize power delivery from anexternal power source to a battery by modifying input voltage andbattery charge current (or input current) based on a variety ofoperational charging parameters including, but not limited to,temperature, duty cycle, and current limiting, for example.

FIG. 2 illustrates an electronic device with a battery charging systemaccording to an embodiment. Electronic device 210 may include arechargeable battery 220. Battery 220 may provide power to variousinternal circuits such as one or more processors 211, communicationscircuits 212 (e.g., RF communications such as Wifi, cellular, Bluetooth,and global positioning systems (GPS)), input/output circuits 213 such asdisplays (e.g., touch screens), audio inputs and outputs and haptics,and various other system electronics 214, for example. Embodiments ofelectronic device 210 may include a cellular phone (e.g., a smartphone), tablet computer, or other battery operated electronic devices assmall as a watch or biometric sensor (e.g., a fitness electronic device)to larger devices (systems) operating off one or more rechargeablebatteries.

In some situations, electronic device 210 may receive power from anexternal power source 201. For example, an external power source 201 maybe coupled to electronic device 210 over one or more electricallyconductive wires 250 (e.g. cable), which may plug into connectors 203and 204, for example. External power sources according to certainembodiments may be configured to produce a plurality of differentvoltage values in response to control signals using voltage adjustcircuitry 202 (V_adj). Example external power sources include AC walladapters (wall chargers) or Universal Serial Bus (USB) ports, which mayproduce different voltages at the input of the electronic device inresponse to control signals received over one or more wires 250. Forexample, one technique for causing an AC wall adapter to producedifferent voltages is known as Quick Charge 2.0™ from Qualcomm® whichmay configure an AC wall adapter to produce output voltages of 5 volts,9 volts, 12 volts, and 20 volts, for example, in response to controlsignals communicated over a cable between the electronic device and thewall adapter. Another technique for causing an AC wall adapter toproduce different voltages is known as Quick Charge 3.0™ from Qualcomm®which may configure an AC wall adapter to produce multiple differentoutput voltages that can change in as little as 200 mV steps, forexample, in response to control signals communicated over a cablebetween the electronic device and the wall adapter. Some USB ports mayalso support producing different voltages in response to control signalsreceived from an electronic device, including USB ports supporting USBPower Delivery over USB type-C cables, for example. The above exampleexternal power sources are only example applications of the techniquesdescribed herein, which may have applications beyond such systems.

When external power source 201 is coupled to electronic device 210 aninput voltage (Vin) is received by a battery charging circuit 230.Initially, input voltage Vin may have a first voltage value (e.g., 5 v).Embodiments of the present disclosure include configuring batterycharging circuit 230 to produce (e.g., supply and regulate) a particularcharge current (e.g., a desired charge current) into battery 220 orregulate the battery voltage. However, some external power sources maynot be able to exceed a particular maximum desired output power tocharge the battery. Thus, if the initial input voltage value and chargecurrent value, for example, exceed the capabilities of the externalpower source, the desired charge current may not be obtained.Additionally, current from the external power source may cause a voltagedrop across the cable, which may reduce the input voltage value. If theinput voltage value is too low due to the resistive drop to supportproper charging, the charge current may have to be reduced to reduce theinput current and therefore increase the input voltage. Furthermore, ifthe desired charge current and voltage are obtained, the electronicdevice may heat up beyond allowable thermal tolerances. Accordingly, inone aspect, temperature inside the electronic device as well as an inputcurrent limit in the battery charging circuit and/or duty cycle may bemonitored and used to control the voltage and current received from theexternal power source to optimize battery charging, for example.

As illustrated in FIG. 2, a battery charging circuit 230 may be part ofa power management integrated circuit 215 (PMIC), for example. In someembodiments, battery charging circuits may alternatively be stand-alonesystems. In this example, battery charging circuit 230 includes aswitching regulator 231 and loop control circuits 232. Switchingregulator 231 may be a Buck regulator, for example, where Vin is greaterthan Vout. Loop control circuits 232 may control the switching regulatorto produce (e.g., regulate) output voltage or current to the battery,for example. Battery charging circuit 230 further includes detectioncircuits 233, current limit circuits 234, controlled current modecharging and controlled voltage mode charging circuits (CC/CV) 235, dutycycle detection circuits 236, temperature control circuits 237, andtimers 238, for example. Detection circuits may be used to detectvoltages and/or currents (e.g., input voltage and/or input current).Example detection circuits that may be used in certain embodiments aredescribed in more detail below. Current limit circuits 234 may sensecurrent (e.g., input current) and implement input current limiting. Forexample, when the value of the input current exceeds a particularcurrent limit (e.g., which may be programmable), the current limitcircuit may activate and control the switching regulator to maintain theinput current at a particular input current limit value. Current controlcharging and voltage control charging circuits (CC/CV) 235 may be usedto configure the switching regulator to perform controlled currentcharging (e.g., constant current) or controlled voltage charging (e.g.,constant voltage). In some embodiments, loop control circuitry mayinclude a pulse width modulator having an input coupled to multiplecontrol loops, including a input current limit control loop, currentcontrol loop, and voltage control loop (e.g., arranged as a wired OR),so that the battery charger may be configured to charge the batteryusing different control parameters, for example. Duty cycle detectioncircuits 236 may monitor the duty cycle. As described in more detailbelow, when the duty cycle is at a maximum duty cycle, duty cycledetection circuits may be used to reconfigure the charging parameters tooptimize charging. Temperature control circuits 237 may includetemperature monitors and control circuitry. As described below,temperature detectors may be on the same integrated circuit die orexternal to the die to measure skin (e.g., surface) temperature, forexample. Temperature control circuits 237 may include digital circuitsthat receive an indication that a temperature has exceeded one or morethreshold temperatures. As described below, the system may bereconfigured based on temperature to optimize charging. Timers 238 maybe used to control the timing of various charging operations asdescribed further below.

FIG. 3 illustrates a method of charging a battery according to anembodiment. In one embodiment, an input voltage is received in a batterycharging circuit on an electronic device from an external power sourceas shown at 301. The input voltage may have a particular initial voltagevalue (e.g., 5 v). At 302, the battery charging circuit is configured toproduce a charge current (Ichg) having a particular current value (e.g.,3 Amps) into the battery. In some instances, the configured chargecurrent may be a desired charge current, and such current may exceed thecapabilities of the external power source. For example, an externalpower source may be limited to 5 W, but to charge a battery at 3 Ampsmay require 15 W from the supply. Alternatively, resistance in the cableat high currents may cause a voltage drop between the output of theexternal power source (e.g., at connector 204) and the input of thebattery charger (e.g., at connector 203). Accordingly, optimal batterycharging in this configuration may not be able to occur. Embodiments ofthe present disclosure may monitor internal system parameters, such asinput current limit and/or duty cycle, to detect conditions wherebattery charging is suboptimal.

For example, in one embodiment, battery charging circuit monitors inputcurrent limit, duty cycle, or both at 303. For instance, as described inmore detail below, certain embodiments may determine a maximum currentcapability of the external power source to set the input current limit.If the maximum input current is reached, the input current limit circuitis activated (e.g., the switching regulator may be controlled tomaintain the input current below a preset maximum input current limitvalue). In this case, it may be desirable to increase the input voltagefrom the external power sources to increase the input power to thebattery charger, for example, to achieve the desired charge current. Forexample, although the external power source may not reach a higheroutput power at a higher output voltage, the required output currentwill be less to achieve the same output power. This will effectivelyovercome cable and PCB trace IR drops, which will deliver higher powerat the input of the battery charger circuit. Alternatively, if the inputvoltage drops to a level close to the output voltage (e.g., due toresistive drops in the cable), the duty cycle may increase. For example,duty cycle in a Buck switching regulator is: Duty Cycle=Vout/Vin.Accordingly, if the input voltage is too low, the duty cycle may reach amaximum duty cycle, and the system may not be able to produce thedesired charge current. Accordingly, it may be desirable to increase theinput voltage from the external power sources to increase Vin andincrease the charge current to desired levels, for example. Therefore,at 304, the battery charger may generate control signals (e.g., to theexternal power source) to increase the first voltage value of the inputvoltage to at least one second voltage value if either (i) the inputcurrent limit is activated or (ii) the duty cycle reaches a maximum dutycycle, for example. In one embodiment, the battery charger may generatecontrol signals to successively increase the input voltage across aplurality of voltage values until a desired charge current is obtained.For example, in the case of Quick Charge 2.0™, the battery charger maysuccessively increase Vin from 5 v to 9 v, and then to 12 v to producethe desired charge current. In the case of Quick Charge 3.0™, thebattery charger may successively increase Vin above 5 v in 200 mV stepsuntil either the current limit and/or the duty cycle indicate that thedesired charge current is being produced, for example.

At 305, the battery charger may monitor temperature at various locationsof the electronic device. As illustrated in example below, temperaturemay be sensed at one location or multiple different physical locations.For instance, a temperature sensor may be placed external to the PMIC tosense a skin temperature of the electronic device. An externaltemperature sensor positioned to sense skin (e.g., external case)temperature may generate a signal indicating that the skin temperaturehas exceeded one or more predefined threshold temperatures, each ofwhich may be programmable, for example. Similarly, a temperature sensormay be implemented on the same substrate as PMIC to sense a dietemperature of the PMIC (or on the die of another device). A temperaturesensor positioned to sense die temperature may similarly generate asignal indicating that the die temperature has exceeded a predefinedthreshold temperature, which may also be programmable, for example. Inone embodiment, sensing the temperature inside the electronic devicecomprises a logical OR of a skin temperature signal and a dietemperature signal so that the system is regulated within safe operatingranges for both external temperature requirements and limits of theintegrated circuits. Embodiments of the present disclosure may adjustthe input voltage and current limit to maintain temperature below athreshold temperature or within a particular temperature range at 306.As illustrated below, example implementations may use multipletemperature readings to activate different charging procedures tooptimize charging based on temperature.

FIG. 4A illustrates a method of charging a battery according to anotherembodiment. At 401 an external power source with configurable outputvoltage is connected to an electronic device. At 402, a battery chargingcircuit in the electronic device determines the type of power source andthe input voltage value. An example of automatic power source detection(APSD) is illustrated below. At 403, the battery charging circuitdetermines a maximum current capability of the external power source andsets an input current limit. An example of an automatic input currentlimit (AICL) circuit is illustrated below. At 404, battery chargingbegins and the battery is charged using the input voltage value. Thebattery charger may be configured to produce a particular desiredbattery charge current. At 405, the input current limit and/or dutycycle may be monitored. If the battery charger input current limit isactivated or if a maximum duty cycle is reached, then the batterycharger may generate control signals to successively increase the inputvoltage across a plurality of voltage values until the desired chargecurrent is obtained at 406. At 407, the temperature is sensed (e.g.,skin and/or die temperature). At 408, if the temperature increases abovea threshold temperature, then the battery charger may cause the externalpower source to decrease the input voltage value. This will reduce powerlosses in the battery charger IC and subsequently reduce temperature. Insome embodiments, the battery charger may generate control signals tosuccessively decrease the input voltage across a plurality of voltagevalues until the temperature decreases below the threshold temperature.

Different external power sources may have different voltage adjustmentcapabilities. For example, different voltage values for some externalpower sources may differ by more than 1 volt (e.g., 5 v, 9 v, and 12 v).Alternatively, other power sources may have very fine voltageresolutions so that different voltage values differ by less than onevolt (e.g., 200 mV steps). Accordingly, different embodiments of thepresent disclosure may detect an external power source type andimplement input voltage and input current limit adjustments in differentsequences. In one embodiment, a battery charger may decrease the inputcurrent limit across a plurality of input current limit values todecrease the temperature below the threshold temperature aftergenerating control signals to decrease the input voltage from theexternal power source. For power sources with the ability to adjust theinput voltage in small steps (e.g., less than 1 volt), it may beadvantageous to adjust the input voltage before adjusting the currentlimit settings. Alternatively, for power sources that have limitedvoltage adjustment capability (e.g., greater than 1 volt), it may beadvantageous to adjust the input current limit settings before adjustingthe input voltage. This way, the available input power can be changed ina more continuous manner. Accordingly, in another embodiment, thebattery charger may decrease the input current limit across a pluralityof input current limit values to decrease the temperature below thethreshold temperature before generating control signals to decrease theinput voltage from the external power source.

Features and advantages of the present disclosure further includeoptimizing charging parameters to reduce power dissipation. FIG. 4Billustrates an example power dissipation curve. One problem created bypower sources with variable voltages is that if the voltage is too high,excessive power can be dissipated during the charging process. FIG. 4Billustrates a power dissipation curve for 12 v charging at 490 and 9 vcharging at 491 across charge current (in Amps) for a typical DC-DC buckconverter charger. It can be seen that there is more power dissipatedacross all charge currents when charging at 12 v versus 9 v.Accordingly, features and advantages of the present disclosure reducethe input voltage values so that power dissipation is reduced.Furthermore, for external power sources with large output voltage steps(e.g., 5 v, 9 v, and 12 v), embodiments of the present disclosure detectwhen charging may occur at a lower voltage, and the system reconfiguresthe voltage and currents so that the system transitions from a firstpower level at a higher input voltage to a second equivalent power levelat a lower input voltage, where the second equivalent power level isequal to the first power level at the higher voltage less the dissipatedpower caused by use of the higher voltage. For example, a batterycharger may be operating at a first higher voltage of 12 v and producinga charge current of 3 A at point A. However, the battery charger may beable to operate at a lower input voltage of 9 v and produce the samecharge current of 3 A with a savings of about 250 mW, for example. Thissavings of 250 mW directly results in a decrease in the skin temperatureof the mobile device.

Features and advantages of some embodiments of the disclosure maydetermine a first power operating point of the charger and reduce theinput voltage to a second power operating point below the first poweroperating point to reduce power dissipation. For example, an initialinput voltage value and charge current value may correspond to a firstpower level at an input of the battery charging circuit. Initially, asdescribed above, if the input current limit is active or if the dutycycle is at a maximum, the input voltage value may be increased to atleast one second voltage value (e.g., from 5 v to 9 v). Increasing thefirst voltage value (e.g., 5 v) to the second voltage value (e.g., 9 v)produces an increase in the charge current to a second current value(e.g., a desired charge current value). The second voltage value and thesecond current value correspond to a second power level at the input ofthe battery charging circuit greater than the first power level. As thebattery charges, the system may reduce the input power to reducetemperature, for example, and it may be possible to also reduce powerdissipation. When the battery charger detects that a lower power levelmay be used (e.g., by sensing input current at a particular inputvoltage level), the battery charger may send control signals to theexternal power source to decrease the input voltage value to a reducedvoltage value and produce a third power level at the input of thebattery charging circuit that is less than the second power level. Theinput voltage value may be decreased such that the third power level isapproximately equal to the second power level less a difference indissipated power between the second voltage value (e.g., Point A in FIG.4B) and the third voltage value (e.g., Point B in FIG. 4B). The point atwhich this input voltage change occurs may be different depending on thevoltages available at the external power source and the availablecurrent limit settings, for example.

FIG. 5 illustrates an example implementation of an electronic devicewith a battery charging system according to another embodiment. In thisexample, an electronic device 510 may be coupled to a variety ofexternal power sources 501 a and 501 b using a USB cable 505. USB cable505 may include a power supply voltage line Vin, a ground (or return)line Gnd, and data lines D+ and D− for carrying data. Embodiments mayfurther include other lines, such as for communicating dedicatedconfiguration information, for example. In this example, electronicdevice 510 may be coupled to an AC power source 501 a using a QuickCharge 3.0™ power adapter 502 (or equivalent) using cable 505 a or aQuick Charge 2.0™ power adapter 503 (or equivalent) using cable 505. ACpower adapters convert AC power from the AC power source into DC voltageand current. Additionally, electronic device 510 may be coupled to USBinterface power source 501 b (e.g., host, hub, etc. . . . ) having aconfigurable DC voltage using cable 505 b. Further, embodiments of thedisclosure may be applicable to other USB capable power sources thatemploy USB Power Delivery.

Electronic device 510 may include a PMIC 515 to provide regulated powersupply voltages to one or more processors 511, communications circuits512, I/O circuits 513, and other circuits as mentioned above. In thisexample, battery charging circuits are included on PMIC 515, although inother embodiments, battery charging circuits may be on anotherintegrated circuit die, for example. In this example, battery chargingcircuits include a Buck switching regulator 520 (i.e., Vsys is less thanVin), an automatic input current limit (AICL) circuit 521, a highvoltage dedicated charge port (HVDCP) detection circuit 522, automaticpower source detection (APSD) circuit 523, temperature detectioncircuits 524, and controlled current/controlled voltage (CC/CV)regulation circuit 525.

Switching regulator circuit 520 includes a high side switch 551 and lowside switch 552, which may both be MOS transistors, inductor 553, outputcapacitor 554, and control circuitry 550, which may include pulse widthmodulation circuits and gate driver circuits to turn switches 551 and552 ON and OFF, for example. An output of the switching regulatorproduces a system voltage Vsys, which may be coupled to battery 560through switch transistor 555 during battery charging and coupled to apower distribution circuit to produce regulated voltages for othersystem circuit blocks. Battery 560 produces voltage Vbatt, which may becoupled through transistor 555 to provide the system voltage when anexternal source is not connected, for example.

AICL circuit 521 may be used to determine a maximum current capabilityof an external power source. One example circuit for performingautomatic input current limiting (AICL) is disclosed in U.S. Pat. No.7,990,106 the content of which is hereby incorporated herein byreference. APSD circuit 523 may be used to determine a type of externalpower source, for example. One example circuit for performing automaticpower source detection (APSD) is disclosed in U.S. Patent PublicationNo. 20120217935 the content of which is hereby incorporated herein byreference. HVDCP circuit 522 may be used to control an external powersource to produce different voltages. One example circuit forcontrolling a high voltage dedicated charge port (HVDCP) is disclosed inU.S. Patent Publication No. 20140122909 the content of which is herebyincorporated herein by reference. Controlled current/controlled voltage(CC/CV) circuit 525 may configure the switching regulator to operate inone or more current control modes (e.g., constant pre-charge current orfast charge current) and a voltage control mode (e.g., constant “float”voltage charging). One example circuit for performing controlled voltageand controlled current charging is disclosed in U.S. Pat. No. 7,880,445the content of which is hereby incorporated herein by reference.Temperature detection circuits 524 may include analog to digitalconverters (ADC) or comparators to receive digital or analog temperaturesensor signals, respectively, and either translate the digitaltemperature sensor signals into temperature data or compare the analogtemperature sensor signals against reference values to determine if atemperature is above or below one or more thresholds, for example. Inone example embodiment, a temperature sensor may comprise adiode-connected bipolar junction transistor (BJT) or a thermistor.

In this example, optimized charging may be implemented using digitallogic 530 in communication with the above mentioned components. Here, acontrol algorithm 531 for charging the battery is implemented as part ofdigital logic 530. However, it is to be understood that otherembodiments may implement the methods and techniques described hereinusing an algorithm operating on a processor in communication with hereindescribed circuit components and configured with software to perform thetechniques described herein. For example, referring to FIG. 2, someembodiments may include a processor configured with computer executablecode, where hardware sensors, detectors, and/or monitor circuits triggerinterrupts that may be used by the executable software code to generatethe control signals to adapter output voltage. For example, an activatedinput current limit or the maximum duty cycle may trigger one or moreinterrupts that cause the processor to generate the control signals forchanging the adapter voltage received by an electronic device forcharging a battery. In the example shown in FIG. 5, digital logic 530may further include timers 533 and temperature control 532. Digitallogic 530 may receive temperature information from temperature detectioncircuits 524. Digital logic 530 may include logic for supporting theAPSD circuits, AICL circuits, and HVDCP circuits, for example. Anexample implementation of digital logic 530 is presented below. In thisexample, the digital logic is shown as residing on the same integratedcircuit as the battery charging hardware (i.e., on the PMIC), but inother embodiments, the digital logic may reside on a differentintegrated circuit than the battery charging hardware.

FIG. 6 illustrates an example method of charging a battery according toan embodiment. At 601, a cable from an external power source may beinserted into a cable input of an electronic device. At 602, anautomatic power source detection procedure is run. At 603, a dedicatedcharge port (DCP), such as a wall adapter, is detected. At 604, theadapter type is detected. In this example, the detected adapter type isa Quick Charge 3.0™ adapter. At 605, automatic input current limitprocess is performed to determine the maximum charge current availablefrom the charger and set a current limit in the charger. For example, ifthe adapter maximum output current is less than a maximum possible inputcurrent to charge the battery, the system may set a current limit so theinput current does not exceed that maximum output current from theadapter. At 606, the charger is enabled and battery charging begins.

As mentioned above, some example embodiments may monitor duty cycle andcurrent limit and successively increase the power supply voltage to thebattery charger until a desired battery charge current is obtained. If amaximum duty cycle is detected, or if input current limiting isactivated, at 607, then the system may perform an initial thermal checkat 608. If the temperature (e.g., of the die or case) is below athreshold temperature, OTST1, then the system may determine if thevoltage can be increased at 609. If the adapter is at its' highestvoltage (e.g., 12 v), then the process returns to 607. However, if theadapter is below 12 v, then the adapter voltage, Vadp, is increased at610. In some embodiments, it may be advantageous to run the AICL processafter each voltage adjustment to make sure that the adapter's poweroutput is not decreasing as its output voltage increase. Accordingly, inthis example, AICL is run at 611, and the maximum duty cycle and inputcurrent limit is checked again at 607.

Features and advantages of the present disclosure include monitoringtemperature and adjusting input voltage and/or an input current limit tomaintain the temperature below a threshold or within a window. In thisexample, if the duty cycle is not at a maximum and the input currentlimit is not active at 607 (or if the temperature is above thresholdOTST1 at 608), the system may enter a process where the temperatureinside the electronic device is sensed and control signals are generatedto decrease the value of the input voltage when the temperatureincreases above a threshold temperature, OTST2, for example. In thisexample implementation, the system determines if the temperature exceedsa threshold temperature, OTST2, at 612. If the temperature is belowOTST2, then the system determines if the temperature is below anotherthreshold at 612, which in this example is OTST1. If the system is belowOTST2 and above OTST1 (e.g., within a “temperature range” or“temperature window”), then charging continues at the existing chargecurrent and adapter voltage, Vadp. However, if the temperature exceedsOTST2, then the system may successively decrease the adapter voltage,Vadp. In this example, the temperature is first compared against amaximum “over-temperature” limit at 614. If the temperature is abovethis limit, then the input current limit is decreased at 622 to apredetermined safe input current limit (here, to 500 mA) and the inputvoltage, Vadp, is decreased at 623 to a predetermined safe input voltage(here, to 5 v). However, if the temperature is below theover-temperature limit at 614, then the adapter voltage is successivelydecreased at 616 unless it is at a minimum power source voltage, whichin this example is 5 v. In this example, Vadp may be decreased in 200 mVsteps, and the system may proceed through steps 613, 612, 614, 615, and616 until the temperature is below OTST2, for example.

The present example may reduce the input voltage value of Vadp beforereducing the input current limit. For example, because Vadp isadjustable in 200 mV steps, it may be advantageous to reduce Vadp beforethe current limit to reduce dissipated power while still providing thedesired charge current. This is because the DC-DC converter in thebattery charger will incur higher switching losses at higher inputvoltage levels. Here, when Vadp is 5 v, as determined at 615, the systemmay start reducing the input current limit at 617 until the temperatureis below OTST2, as determined at 618, for example. Once Vadp is at 5 vand the input current limit has been reduced, the system may continuecharging as long as the temperature is within a temperature range (orwindow) below OTST2 and above OTST1. If the temperature falls belowOTST1 while the system is at a minimum power supply input voltage of 5v, then the system may determine if the input current is at the inputcurrent limit at 620, and if so, then increase the input current limitat 621 (e.g., successively until the temperature increases above OTST1).If the input current is less than the input current limit at 620, thenthe system may increase Vadp at 609, for example, until the maximum dutycycle or input current limit are reached. When Vadp and the inputcurrent are such that the maximum duty cycle and input current limit arenot triggered, and when the temperature is below OTST1 (the lowerthermal threshold) at 613, the system may enter a mode where constantvoltage is detected and power is reduced at 690. The process performedat 690 is described in more detail below with reference to FIGS. 9A and9B, for example.

FIG. 7 illustrates another example method of charging a batteryaccording to another embodiment. Similar to FIG. 6, steps 701-706 aresimilar to steps 601-606 except in this example a Quick Charge 2.0™adapter is detected. Such an adapter may be configured to producediscrete voltages of 5 v, 9 v, and 12 v, for example. One problem withdifferences between the input voltages to the charger is that the systemmay dissipate more power at higher voltages, which may be necessary toproduce desired charge currents. One challenge with external sourceshaving large voltage differences between settings is optimallyconfiguring the system to produce a desired charge current into thebattery with minimum power dissipation losses. In this example, thesystem may separately determine if the input current limit is active at707 and whether the maximum duty cycle has been reached at 708. If theinput current limit has been reached at 707, the system may send controlsignals to reduce the voltage value from the adapter, Vadp. In thisexample, if the maximum duty cycle has been reached at 708, the systemmay advantageously set a flag indicating the reason why the inputvoltage was incremented at 709 (e.g., INC_REAS=DC; i.e., the inputvoltage Vadp was increased because the duty cycle was at a maximum).Similar to the example in FIG. 6, the system may determine if thetemperature is below threshold OTST1 at 710, and if so successivelyincrease Vadp at steps 711-715 and run AICL at 780. Once the inputvoltage Vadp is set so that the system is not at maximum duty cycle andnot input current limiting, charging continues as long as thetemperature remains within a range set by OTST1 and OTST2. If thetemperature exceeds threshold OTST2, then the maximum temperature, Tmax,is checked at 718 (at input current limit and Vadp reduced at 732 as inFIG. 6 if above Tmax).

The present example implementation illustrates another advantage of someembodiments. In this example, the input current limit is decreasedacross a plurality of input current limit values to decrease thetemperature before the decreasing the value of Vadp. For instance, at719 and 732 the system determines if Vadp can be decreased (e.g., if itis at either 12 v or 9 v). If Vadp is at a maximum voltage (e.g., 12 v)at 719, for example, the input current, Iin, is compared to a firstinput current threshold (e.g., Iin_9 v_switch) at 720. If the inputcurrent is greater than the first input current threshold, then thesystem may reduce the input current limit at 727. If the temperatureremains above OTST2 at 728, then the system repeats steps 718, 719, and720 until the input current is below the first input current threshold.When the input current is equal to the first input current threshold,Iin_9 v_switch, the adapter voltage may be decreased to the next step.Advantageously, the first input current threshold, Iin_9 v_switch,corresponds to an input power level at a first value of Vadp (e.g., 12v) where there is an equivalent input power level at a second value ofVadp (e.g., 9 v) that produces the desired battery charge current.However, the equivalent input power level may be lower than the previousinput power level because there is less power dissipation in thecharger. Accordingly, Vadp may be decreased such that a new input powerlevel (or final input power, Pi_final) at the lower value of Vadp isapproximately equal to the previous input power level (or initial inputpower, Pi_init) at a higher value of Vadp less (i.e., minus) adifference in dissipated power (e.g., Pi_init=Pi_final−Pdiss). The powerdissipation eliminated by transitioning to a lower value of Vadp can beseen in FIG. 4B. The above described example senses the input currentand may compare the input current to one or more thresholds to triggerthe transition to decrease Vadp, for example. Referring again to FIG. 7,if Iin is less than or equal to current threshold Iin_9 v_switch, thenthe system may check the flag INC_REAS (described above). If the dutycycle was the cause of the increase in Vadp at 714-715, then Vadp isdecreased at 722. If the duty cycle was not the cause of the increase inVadp at 714-715, then the input current limit is decreased further.Advantageously, independently determining that the battery charger is ata maximum duty cycle and the current limit is not activated (e.g., andsetting flag INC_REAS) allows the system to distinguish betweensituations where current through the cable is causing a voltage drop(i.e., Vadp is sufficiently high for charging but the current is toohigh) versus situations where Vadp is not high enough to achieve thedesired charge current for a given adapter output current. In thepresent example, if the duty cycle was the cause of the increase in Vadp(INC_REAS=DC), then the current from the adapter is decreased at 727 bydecreasing the input current limit. If the temperature remains aboveOTST2 (at either 716 or 728), then the system returns to 719 to decreasethe input current limit and/or Vadp until the temperature is within thetemperature window above OTST1 and below OTST2, for example.

FIG. 8 illustrates a block diagram of a circuit to control batterycharging according to an embodiment. FIG. 8 is one example of digitallogic that may implement the algorithms in FIGS. 6 and 7, for example.While the present example is implemented in digital logic, it is to beunderstood that the disclosed techniques may be implemented in analogcircuits or on a digital processor, for example. In this example,digital control circuits may include an APSD control circuit 802, HVDCPcontrol circuit 803, thermal regulation control circuit 804, AICLcontrol circuit 805, trigger control circuit 806, input current limitcalculator 807, and timer 808.

APSD control circuit 802 may interface with external power source 801 todetect the external power source. HVDCP control circuit 803 may generatecontrol signals to increase and/or decrease a voltage value of an inputvoltage from external power source 801. In this example, HVDCP includesan APSD interface 811 to produce a control signal Vadp_change, whichcauses APSD control circuit 802 to generate control signals to negotiatea change in the external power source voltage. HVDCP control circuit 803may include a VADP increase processor 812 to monitor an input currentlimit active signal (Current Limiting Qual) and a maximum duty cyclesignal (Max Duty Cycle Qual) to trigger changes in Vadp, for example.

AICL control circuit 805 may perform AICL functions, which may includesetting an input current limit in response to temperature controlsignals from thermal regulation control circuit 804, trigger signalsfrom trigger circuit 806, and max/min ICL signal from ICL limitcalculation circuit 807. AICL control circuit 805 may include atemperature offset circuit 822 for offsetting an input current limitdetermined by AICL ICL circuit 821.

Trigger control circuit 806 is one example circuit for monitoring aninput current limit and a duty cycle of the battery charging circuit.Trigger circuit 806 receives digital signals indicating a max duty cycleis reached, input current limit is active (e.g., the input current meetsthe set input current limit), and input collapse signal indicating ifthe voltage at the input has dropped out.

Thermal regulation control circuit 804 is one example circuit thatreceives signals indicating a temperature inside the electronic device.In this example, thermal regulation control circuit receives 3 bits forskin temperature (e.g., from an external temperature sensor and anexternal or internal analog to digital converter) and 3 bits for dietemperature in temperature monitor circuit 834. Temperature monitorcircuit 834 may monitor the temperature and generate increase/decreasesignals to temp controller 831. Temp controller 831 may determinewhether to change the input current limit, ICL, or input voltage, Vadp,(as described above) using decision circuit 833 and produce ICLincrement signal and ICL decrement signal (e.g., to ICL temp offsetcircuit 832) and adapter decrement signal (e.g., to APSD interface 811).Decision circuit 833 may control whether the input voltage is decreasedbefore or after the current limit is reduced, as described above.Accordingly, decision circuit 833 may receive one or more inputs from apower calculator circuit 835 which receives a cable resistance, inputvoltage signal, and ICL signal to determine when to change the inputcurrent limit versus the input voltage, for example. Timer circuits 808may include one or more timers, which may be used to implement aconstant voltage power reduction algorithm, which will now be described.

FIG. 9A illustrates a method of charging a battery during constantvoltage (CV) mode according to an embodiment. During CV charging, chargecurrent gradually reduces as the battery cell voltage increases to thebattery pack voltage. Accordingly, as the charge current decreasesefficiency may be improved by reducing the charger input voltage. Asmentioned above, embodiments of the present disclosure may reduceadapter power during constant voltage charging. For example, in oneembodiment, the system may detect when the temperature is below athreshold temperature (e.g., a lower threshold of a temperature window).Reductions in temperature may be observed when the system transitionsfrom controlled current charging to controlled (or constant) voltagecharging, for example. In one embodiment, a method includes detecting aconstant voltage mode at 901 (e.g., when the temperature falls belowOTST1 in FIGS. 6 and 7). At 902 a timer is set and the system may wait apredefined period of time. At 903 control signals are generated todecrease a present value of the input voltage.

FIG. 9B illustrates another example method to reduce power duringconstant voltage charging. At 910 the system determines if constantvoltage mode is active. At 911 a 5 minute timer is checked (e.g., thesystem waits 5 min if CV charging is active). At 912 the system detectsif the input voltage is above a minimum value (e.g., 5 v), and if so,the system decreases the input voltage (e.g., Vadp is reduced by 200 mV)at 913. Subsequently, the timer will be reset and upon each additionalexpiration, the adapter voltage will be decremented. If any of the abovesteps are not applicable, then the system may return to current limitand duty cycle monitoring and may increase Vadp as described above(e.g., Vadp may be increased again after the temperature falls belowthreshold OTST1).

The above description illustrates various embodiments of the presentdisclosure along with examples of how aspects of the particularembodiments may be implemented. The above examples should not be deemedto be the only embodiments, and are presented to illustrate theflexibility and advantages of the particular embodiments as defined bythe following claims. Based on the above disclosure and the followingclaims, other arrangements, embodiments, implementations and equivalentsmay be employed without departing from the scope of the presentdisclosure as defined by the claims.

What is claimed is:
 1. A circuit to control battery charging,comprising: a power source detection circuit configured to interfacewith a programmable power source; a charge port circuit coupled to thepower source detection circuit, the charge port circuit configured toprovide a control signal to the power source detection circuit toincrease or decrease voltage from the programmable power source; athermal regulation circuit coupled to the charge port circuit, whereinthe thermal regulation circuit comprises a temperature monitor coupledto receive one or more temperature signals, the temperature monitorproviding temperature increase or decrease signals, and a temperaturecontroller coupled to receive the temperature increase or decreasesignals from the temperature monitor, the temperature controllerconfigured to provide signals indicating a change in an input currentlimit or a voltage; and an input current limit circuit coupled to thecharge port circuit, wherein the charge port circuit is configured toprovide the control signal to the power source detection circuit toincrease or decrease the voltage in response to signals from the thermalregulation circuit and the input current limit circuit.
 2. The circuitof claim 1, wherein the charge port circuit comprises a power sourcedetection circuit interface coupled to provide the control signals tothe power source detection circuit; and a processor coupled to the powersource detection circuit interface that is configured to monitor aninput current limit active signal and a maximum duty cycle signal andprovide an indication to the power source detection circuit interface toproduce the control signal to the power source detection circuit.
 3. Thecircuit of claim 1, further including an input current limit calculatorcoupled to the power source detection circuit, the input current limitcalculator providing a current limit range to the input current limitcircuit in response to a type of programmable power supply received fromthe power source detection circuit.
 4. The circuit of claim 1, furtherincluding a trigger control circuit coupled to the charge port circuit,the trigger control circuit configured to monitor an input current limitand a duty cycle of a battery charging circuit and provide triggersignals to the charge port circuit in response to reaching a maximumduty cycle or determining an input current limit is active.
 5. Thecircuit of claim 1, further including a power calculator coupled toreceive a cable resistance, an input voltage signal, and an inputcurrent limit (ICL) signal, and wherein the temperature controllerincludes a decision circuit that is configured to receive a decisionsignal from the power calculator and control whether to produce an ICLincrement/decrement signal or a voltage increment/decrement signal tothe input current limit circuit.
 6. The circuit of claim 1, furtherincluding a timer coupled to the charge port circuit, the timerconfigured to provide a timing signal to the charge port circuit.
 7. Thecircuit of claim 6, wherein the charge port circuit is configured toreceive the timing signal and provide signals to the power sourcedetection circuit to implement a gradual reduction in the voltage fromthe programmable power supply.
 8. The circuit of claim 7, wherein thevoltage is reduced as a charging current is reduced.
 9. The circuit ofclaim 7, wherein the voltage is reduced at timed intervals.
 10. Acircuit to control battery charging, comprising: a power sourcedetection circuit configured to interface with a programmable powersource; a charge port circuit coupled to the power source detectioncircuit, the charge port circuit configured to provide a control signalto the power source detection circuit to increase or decrease voltagefrom the programmable power source; a thermal regulation circuit coupledto the charge port circuit; an input current limit circuit coupled tothe charge port circuit; and a trigger control circuit coupled to thecharge port circuit, wherein the charge port circuit is configured toprovide the control signal to the power source detection circuit toincrease or decrease the voltage in response to signals from the thermalregulation circuit and the input current limit circuit, and the triggercontrol circuit configured to monitor an input current limit and a dutycycle of a battery charging circuit and provide trigger signals to thecharge port circuit in response to reaching a maximum duty cycle ordetermining an input current limit is active.
 11. The circuit of claim10, further including an input current limit calculator coupled to thepower source detection circuit, the input current limit calculatorproviding a current limit range to the input current limit circuit inresponse to a type of programmable power supply received from the powersource detection circuit.
 12. The circuit of claim 10, wherein thethermal regulation circuit comprises a temperature monitor coupled toreceive one or more temperature signals, the temperature monitorproviding temperature increase or decrease signals; and a temperaturecontroller coupled to receive the temperature increase or decreasesignals from the temperature monitor, the temperature controllerconfigured to provide signals indicating a change in an input currentlimit or a voltage.
 13. The circuit of claim 12, further including apower calculator coupled to receive a cable resistance, an input voltagesignal, and an input current limit (ICL) signal, and wherein thetemperature controller includes a decision circuit that is configured toreceive a decision signal from the power calculator and control whetherto produce an ICL increment/decrement signal or a voltageincrement/decrement signal to the input current limit circuit.
 14. Thecircuit of claim 10, further including a timer coupled to the chargeport circuit, the timer configured to provide a timing signal to thecharge port circuit.
 15. A circuit to control battery charging,comprising: a power source detection circuit configured to interfacewith a programmable power source; a charge port circuit coupled to thepower source detection circuit, the charge port circuit configured toprovide a control signal to the power source detection circuit toincrease or decrease voltage from the programmable power source; athermal regulation circuit coupled to the charge port circuit; an inputcurrent limit circuit coupled to the charge port circuit; and a timercoupled to the charge port circuit, the timer configured to provide atiming signal to the charge port circuit, wherein the charge portcircuit is configured to provide the control signal to the power sourcedetection circuit to increase or decrease the voltage in response tosignals from the thermal regulation circuit and the input current limitcircuit.
 16. The circuit of claim 15, wherein the charge port circuitcomprises a power source detection circuit interface coupled to providethe control signals to the power source detection circuit; and aprocessor coupled to the power source detection circuit interface thatis configured to monitor an input current limit active signal and amaximum duty cycle signal and provide an indication to the power sourcedetection circuit interface to produce the control signal to the powersource detection circuit.
 17. A circuit to control battery charging,comprising: a power source detection circuit configured to interfacewith a programmable power source; a charge port circuit coupled to thepower source detection circuit, the charge port circuit configured toprovide a control signal to the power source detection circuit toincrease or decrease voltage from the programmable power source; athermal regulation circuit coupled to the charge port circuit; an inputcurrent limit circuit coupled to the charge port circuit; and an inputcurrent limit calculator coupled to the power source detection circuit,the input current limit calculator providing a current limit range tothe input current limit circuit in response to a type of programmablepower supply received from the power source detection circuit, whereinthe charge port circuit is configured to provide the control signal tothe power source detection circuit to increase or decrease the voltagein response to signals from the thermal regulation circuit and the inputcurrent limit circuit.